1. Field of the Invention
The present invention relates to an X-ray source holding apparatus which rotatably holds an X-ray tube such that the X-ray irradiation direction can be adjusted. More specifically, the present invention relates to an X-ray source holding apparatus which locks the posture of an X-ray tube, to thereby fix the X-ray irradiation direction.
2. Description of the Related Art
The X-ray source holding apparatus of the above type is incorporated in an X-ray diagnostic system, and is employed by an X-ray tube rotating mechanism which varies the posture of an X-ray tube, i.e., the X-ray irradiation direction.
An X-ray diagnostic system suspended from a ceiling is well known in the art. In this type of X-ray diagnostic system, a guide rail is installed on the ceiling, and a slider which is slidable along the guide rail is provided. A telescopic holding arm is suspended from the slider, and a holding unit incorporating an X-ray tube rotating mechanism is coupled to the lower end of the holding arm. A rotatable disk, which is rotatable around a horizontal axis parallel to the guide rail, is coupled to one face of the holding unit. A frame, on which an X-ray tube and a diaphragm device are supported, is attached to the rotatable plate.
When the above X-ray diagnostic system is in use, it is necessary to change the X-ray irradiation direction (i.e., the posture of the X-ray tube) depending on the case where a subject is standing and the case where the subject is lying on an examination bed or the like. To change the X-ray irradiation direction, the rotatable disk is manually rotated around the horizontal axis and locked at one of positions determined beforehand. With the rotatable disk locked in this manner, X-rays are irradiated in a desirable direction.
To lock the rotatable disk at a desirable position, the rotatable disk has positioning holes formed therein, and the holding unit incorporates a lock mechanism. The lock mechanism is made up of a lock pin, and a spring which urges the lock pin to the rotatable disk and inserts it into one of the positioning holes. When the X-ray irradiation direction coincides with one of directions corresponding to the predetermined locking positions, the lock pin protrudes from the side face of the holding unit and is inserted into one of the positioning holes. As a result, the rotation of the rotatable disk is prohibited, and the X-ray irradiation direction is fixed.
To change the X-ray irradiation direction, the operator manually pulls the lock pin out of the positioning hole against the urging force of the spring, to thereby unlock the rotatable disk. Then, the operator manually rotates the rotatable disk to change the X-ray irradiation direction. If the operator wants to fix the X-ray irradiation direction, he or she further rotates the rotatable disk until the lock pin urged by the spring is inserted to another positioning hole. As is understood from this, the operator has to manually pull the lock pin out of the positioning hole and rotate the rotatable disk, when the operator wants to change the X-ray irradiation direction (i.e., the posture of the X-ray tube). Such manual operations are annoying to the operator.
In general, three positioning holes are formed in the circumferential regions of the rotatable disk such that they are shifted from each other by an angle of 90.degree.. Let it be assumed that such a general type rotatable plate has to be rotated 180.degree. from one locked position to another. In this case, the operator pulls the lock pin from the positioning hole and rotates the rotatable disk. When the disk has just been rotated 90.degree., the lock pin engages with the positioning hole 90.degree. shifted from the first positioning hole. Thus, the operator pulls the lock pin out of the positioning hole once again, and further rotates the plate until the lock pin engages with the positioning hole 180.degree. shifted from the first positioning hole. Obviously, this operation is troublesome to the operator. If the rotatable disk has four or more positioning holes, the operation is more troublesome since the operator has to repeatedly release the lock pin from the positioning holes during the rotation of the disk.
As has been described, the X-ray source holding apparatus incorporated in the above X-ray diagnostic system requires the operator to manually pull the lock pin from the positioning holes of the rotatable disk when the operator rotates the rotatable disk to change X-ray irradiation directions. Such a manual operation required for unlocking the rotatable disk is very troublesome to the operator.